1. Field of the Invention
The present invention is related to a method of managing a mobility management layer in a mobile device, and more particularly, to a method of managing a mobility management layer in a mobile device with improved system efficiency.
2. Description of the Prior Art
According to 3GPP (3rd Generation Partnership Project) mobile communication structure, the wireless interface protocol structure of a mobile device includes three layers: a physical layer, a data link layer, and a network layer. The data link layer includes a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a medium access control (MAC) layer. The network layer includes a radio resource control (RRC) layer, a mobility management (MM) layer and a connection management (CM) layer.
The RLC layer is configured to provide services including protocol data unit (PDU) transmission, automatic retransmission request (ARQ) correction, concatenation, service data unit (SDU) segmentation/reassembly/deletion, sequential PDU transmission, duplicative detection, protocol error detection, and protocol reestablishment.
The MAC layer is configured to provide services including hybrid automatic repeat request (HARQ) error correction and transmission time interval (TTI) bundling transmission.
The CM layer is configured to provide call controls, including establishing connection, selecting connection type (voice or fax) and releasing connection, and manage supplementary service (SS) and short message service (SMS).
The RRC layer is configured to maintain connection, establish/release communication channel, and manage power control.
The MM layer is configured to handle user verification, signal encoding and all mobility-related functions so that the network may be informed of the current location of the mobile device.
According to current 3GPP specifications, after entering State 9, the MM layer has a RR connection to its peer entity in the network, but no MM connection is established. The mobile device is passive, awaiting further commands from the network. In the prior art, if the network somehow fails to respond, the MM layer of the mobile device may stay in State 9 and thus is unable to provide other services.